shock - OHCM Flashcards
Essence
Circulatory failure resulting in inadequate organ perfusion. Often defi ned
by low BP—(SBP) systolic 2mmol/L.
MAP = cardiac output (CO) ≈ systemic vascular resistance (SVR). CO = stroke volume
≈ heart rate. So shock can result from inadequate CO or a loss of SVR, or both.
Signs:
Low GCS/agitation, pallor, cool peripheries,
tachycardia, slow capillary refi ll, tachypnoea, oliguria.
causes of inadequate CO
1 -hypovolaemia
2 - pump failure
causes of hypovolaemia
Bleeding: trauma, ruptured aortic aneurysm, GI bleed.
• Fluid loss: vomiting, burns, ‘third space’ losses, eg pancreatitis, heat exhaustion.
causes of pump failure
• Cardiogenic shock, eg ACS, arrhythmias, aortic dissection, acute valve failure.
• Secondary causes, eg pulmonary embolism, tension pneumothorax, cardiac
tamponade.
causes of Peripheral circulatory failure (loss of SVR)
1 - sepsis 2 - anaphylaxis 3 - neurogenic 4 - endocrine failure 5 - other - Drugs, eg anaesthetics, antihypertensives. Inability to use oxygen, eg cyanide poisoning
cause of Septic shock:
Infection with any organism can cause acute vasodilation from infl ammatory
cytokines. Gram –ves can produce endotoxin, causing sudden and severe
shock but without signs of infection (fever, raised WCC). Classically patients with
sepsis are warm & vasodilated, but may be cold & shut down. Other diseases, eg pancreatitis, can give a similar picture associated with the inflammatory cascade.
possible causes of neurogenic shock
Eg spinal cord injury, epidural or spinal anaesthesia.
possible causes of endocrine failure shock
Addison’s disease, p846 or hypothyroidism
assessment of shock
ABCDE (p793) With shock we are dealing primarily with ‘C’ so get large-bore IV access ≈ 2 and check ECG for rate, rhythm (very fast or very slow will compromise cardiac output), and signs of ischaemia.
Management - If BP unrecordable, call the cardiac arrest team.
General review: Cold and clammy suggests cardiogenic shock or fl uid loss. Look for
signs of anaemia or dehydration, eg skin turgor, postural hypotension? Warm and well perfused, with bounding pulse points to septic shock. Any features suggestive of anaphylaxis—history, urticaria, angio-oedema, wheeze?
CVS: usually tachycardic (unless on beta-blocker, or in spinal shock—OHCS p772) and hypotensive.
But in the young and fi t, or pregnant women, the systolic BP may remain
normal, although the pulse pressure will narrow, with up to 30% blood volume depletion.
Diff erence between arms (>20mmHg)—aortic dissection?
JVP or central venous pressure: If raised, cardiogenic shock likely.
Check abdomen: Any signs of trauma, or aneurysm? Any evidence of GI bleed?
management of septic shock
Management - If BP unrecordable, call the cardiac arrest team.
• Ideally take cultures before antibiotics (2 ≈ peripheral blood culture plus, eg,
urine, sputum, CSF) but do not delay starting treatment!
• Give antibiotics within fi rst hour, choice depends on local policy and suspected
source. Empirical if no clear source, eg Tazocin® (4.5g tds) + gentamicin (eg
5mg/kg od; see p766) + vancomycin (1g/12h IVI) if MRSA. Adjust doses in CKD.
• After fluid bolus of 20mL/kg crystalloid (or 7mL/kg colloid) repeat BP and ABG.
If SBP remains 4mmol/L then consider referral to ICU for early
goal-directed therapy5—aim CVP 8–12, MAP >65mmHg, UO >0.5mL/kg/h.
• Low-dose steroids may improve BP but do not improve mortality, recombinant
activated protein C does not improve outcome and has been withdrawn from
the market.
management of hypovolaemic shock
Management - If BP unrecordable, call the cardiac arrest team.
Identify and treat underlying cause. Raise the legs.
• Give fl uid bolus 10–15mL/kg crystalloid or 3–5mL/kg colloid, if shock improves,
repeat, titrate to HR (aim 90) and UO (aim >0.5mL/kg/h)
• If no improvement after 2 boluses, consider referral to ICU.
management of haemorrhagic shock
Stop bleeding if possible. See TABLE for grading.
• If still shocked despite 2L crystalloid or present with class III/IV shock (see table) then crossmatch blood (request O Rh–ve in an emergency, see p342)
• Give FFP alongside packed red cells (1 : 1 ratio) and aim for platelets >100 and fibrinogen >1. Discuss with haematology early.
management of shcok when cause is unclear
If cause unclear: treat as hypovolaemia—the
most common cause, and reversible.
classes of shock severity
class 1 - 4 (worst), defined by phys variables to give predicted blood loss
